[Berlin-wireless] VPN03 MTU-Probleme

[Amadeus Alfa]

Hallo *,

wir haben MTU-Probleme auf dem VPN03-Link festgestellt, die sich wie folgt
äußern:

# Ping via ISP (eth0)

S ping -I eth0 -s 1472 -c1 212.227.222.8
PING 212.227.222.8 (212.227.222.8) from 78.46.48.196 eth0: 1472(1500) bytes
of data.
1480 bytes from 212.227.222.8: icmp_req=1 ttl=55 time=7.97 ms

S ping -I eth0 -s 5000 -c1 212.227.222.8
PING 212.227.222.8 (212.227.222.8) from 78.46.48.196 eth0: 5000(5028) bytes
of data.
5008 bytes from 212.227.222.8: icmp_req=1 ttl=55 time=8.10 ms

# Ping via VPN03 (ovpnextvpn03)

S ping -I 172.31.240.39 -s 1418 -c1 212.227.222.8
PING 212.227.222.8 (212.227.222.8) from 172.31.240.39 : 1418(1446) bytes of
data.
1426 bytes from 212.227.222.8: icmp_req=1 ttl=54 time=37.8 ms

S ping -I 172.31.240.39 -s 1419 -c1 212.227.222.8
PING 212.227.222.8 (212.227.222.8) from 172.31.240.39 : 1419(1447) bytes of
data.
--- 212.227.222.8 ping statistics ---
1 packets transmitted, 0 received, 100% packet loss, time 0ms

S ping -I 172.31.240.39 -s 1472 -c1 212.227.222.8
PING 212.227.222.8 (212.227.222.8) from 172.31.240.39 : 1472(1500) bytes of
data.
--- 212.227.222.8 ping statistics ---
1 packets transmitted, 0 received, 100% packet loss, time 0ms

S ping -I 172.31.240.39 -s 5000 -c1 212.227.222.8
PING 212.227.222.8 (212.227.222.8) from 172.31.240.39 : 5000(5028) bytes of
data.
--- 212.227.222.8 ping statistics ---
1 packets transmitted, 0 received, 100% packet loss, time 0ms
Es gibt also offenbar Probleme bei der max. MTU und infolgedessen auch kein
Reassembling.

Wir verwenden die mitgelieferte VPN03-Standard-Konfiguration für UDP:

# Freifunk Berlin VPN, UDP, Unencrypted, OpenVPN 2.1+
client
dev-type tun
dev ovpnextvpn03
remote vpn03.routers.chemnitz.freifunk.net 1194 udp
nobind
route-nopull
persist-key
ping-restart 15
ca /etc/ffc/service-openvpn/external/vpn03/freifunk-ca.crt
cert /etc/ffc/service-openvpn/external/vpn03/freifunk-ff-chemnitz.crt
key /etc/ffc/service-openvpn/external/vpn03/freifunk-ff-chemnitz.key
ns-cert-type server
comp-lzo no
cipher none
verb 1

Viele Grüße,
Amadeus

--
Vorstand
Freifunk Chemnitz e.V.
Dipl.-Ing. Amadeus Alfa
Mobil: +49 170 6763627

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